Wood laminate articles comprising substituted cellulose ester adhesives and methods relating thereto

ABSTRACT

Wood laminates may comprise a plurality of wood substrates and an adhesive disposed between at least a portion of at least two of the wood substrates, the adhesive comprising a substituted cellulose ester that comprises a cellulose polymer backbone having an organic ester substituent and an inorganic ester substituent that comprises an inorganic, nonmetal atom selected from the group consisting of sulfur, phosphorus, boron, and chlorine. In some instances the adhesive may be substantially formaldehyde-free.

BACKGROUND

The present invention relates to wood laminates produced withsubstituted cellulose ester adhesives, and methods related thereto.

In the production of wood laminates, such as plywood, flooring, andfurniture, a plurality of wood substrates are adhered together using anadhesive. The most common adhesives are urea and melamine formaldehyderesins because they strongly bind to wood substrates. However, it isbelieved that these adhesives may release formaldehyde into thesurrounding environment over time, which is undesirable becauseformaldehyde is a known carcinogen, has a pungent odor, and has beenshown to induce asthma attacks in relatively low doses.

Accordingly, formaldehyde-free wood adhesives are of much interest.However, alternatives, like polyurethane-based wood adhesives, oftenhave less than satisfactory adhesive properties and produce low-qualitywood laminates. Therefore, formaldehyde-free wood adhesives that exhibitadhesive properties comparable to or better than urea and melamineformaldehyde resins would be of value.

SUMMARY OF THE INVENTION

The present invention relates to wood laminates produced withsubstituted cellulose ester adhesives, and methods related thereto.

In one embodiment of the present invention, a wood laminate maycomprise: a plurality of wood substrates; and an adhesive disposedbetween at least a portion of two of the wood substrates, the adhesivecomprising a substituted cellulose ester that comprises a cellulosepolymer backbone having an organic ester substituent and an inorganicester substituent that comprises an inorganic, nonmetal atom selectedfrom the group consisting of sulfur, phosphorus, boron, and chlorine.

In another embodiment of the present invention, a wood laminate maycomprise a wood substrate; a wood veneer; and an adhesive disposedbetween at least a portion of the wood substrate and at least a portionof the wood veneer, the adhesive comprising a substituted celluloseester that comprises a cellulose polymer backbone having an organicester substituent and an inorganic ester substituent that comprises aninorganic, nonmetal atom selected from the group consisting of sulfur,phosphorus, boron, and chlorine.

In yet another embodiment of the present invention, a method maycomprise applying an adhesive to at least a portion of a surface of afirst wood substrate; placing a second wood substrate to the portion ofthe surface of the first wood substrate; and drying the adhesive. Theadhesive may, in some embodiments, comprise a solvent and a substitutedcellulose ester that comprises a cellulose polymer backbone having anorganic ester substituent and an inorganic ester substituent thatcomprises an inorganic, nonmetal atom selected from the group consistingof sulfur, phosphorus, boron, and chlorine.

In another embodiment of the present invention, plywood may comprise atleast two wood veneers; and an adhesive disposed between at least aportion of two of the wood veneers, the adhesive comprising asubstituted cellulose ester that comprises a cellulose polymer backbonehaving an organic ester substituent and an inorganic ester substituentthat comprises an inorganic, nonmetal atom selected from the groupconsisting of sulfur, phosphorus, boron, and chlorine.

In yet another embodiment of the present invention, a piece of furnituremay comprise a fiberboard; a wood veneer; and an adhesive disposedbetween at least a portion of the fiberboard and at least a portion ofthe wood veneer, the adhesive comprising a substituted cellulose esterthat comprises a cellulose polymer backbone having an organic estersubstituent and an inorganic ester substituent that comprises aninorganic, nonmetal atom selected from the group consisting of sulfur,phosphorus, boron, and chlorine.

In yet another embodiment of the present invention, a piece of furnituremay comprise at least two pieces of lumber; and an adhesive disposedbetween at least a portion of at least two of the pieces of lumber, theadhesive comprising a substituted cellulose ester that comprises acellulose polymer backbone having an organic ester substituent and aninorganic ester substituent that comprises an inorganic, nonmetal atomselected from the group consisting of sulfur, phosphorus, boron, andchlorine.

In yet another embodiment of the present invention, a piece of flooringmay comprise a wood veneer; a decorative wood veneer comprising avisually appealing surface; and an adhesive disposed between at least aportion of the wood veneer and at least a portion of the decorative woodveneer such that the visually appealing surface is visible, the adhesivecomprising a substituted cellulose ester that comprises a cellulosepolymer backbone having an organic ester substituent and an inorganicester substituent that comprises an inorganic, nonmetal atom selectedfrom the group consisting of sulfur, phosphorus, boron, and chlorine.

In yet another embodiment of the present invention, wood trim maycomprise a fiberboard; a decorative wood veneer comprising a visuallyappealing surface; and an adhesive disposed between at least a portionof the fiberboard and at least a portion of the decorative wood veneersuch that the visually appealing surface is visible, the adhesivecomprising a substituted cellulose ester that comprises a cellulosepolymer backbone having an organic ester substituent and an inorganicester substituent that comprises an inorganic, nonmetal atom selectedfrom the group consisting of sulfur, phosphorus, boron, and chlorine.

The features and advantages of the present invention will be readilyapparent to those skilled in the art upon a reading of the descriptionof the preferred embodiments that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of thepresent invention, and should not be viewed as exclusive embodiments.The subject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, as willoccur to those skilled in the art and having the benefit of thisdisclosure.

FIGS. 1A-E provide illustrations of nonlimiting examples of woodlaminate configurations according to at least some embodiments of thepresent invention.

FIG. 2 provides a nonlimiting example of a substituted cellulose estersynthesis route according to at least some embodiments of the presentinvention.

FIG. 3 provides a nonlimiting example of a substituted cellulose estersynthesis route according to at least some embodiments of the presentinvention.

FIG. 4 provides a nonlimiting example of a substituted cellulose estersynthesis route according to at least some embodiments of the presentinvention.

DETAILED DESCRIPTION

The present invention relates to wood laminates produced withsubstituted cellulose ester adhesives, and methods related thereto.

The present invention provides for, in some embodiments, wood laminatesthat comprise substituted cellulose ester adhesives that may, in someembodiments, advantageously be at least substantially formaldehyde-free.As used herein, the term “substantially formaldehyde-free” refers to theadhesive comprising less than 0.01% formaldehyde by weight of theadhesive.

In addition to not having the disadvantages associated withformaldehyde-based adhesives such as those discussed above, theadhesives described herein are advantageously derived from renewablecellulosic sources. Consequently, the adhesive compositions are, to somedegree, earth-friendly in addition to being less noxious. Further,long-term the adhesive compositions described herein, under the properconditions (e.g., in a landfill), may be degradable, and thereby mayenhance the degradability of the wood laminates produced therewith.Accordingly, the adhesive compositions described herein provide for woodlaminates that are thought to be both more health-friendly andenvironmentally-friendly.

It should be noted that when “about” is used in reference to a number ina numerical list, the term “about” modifies each number of the numericallist. It should be noted that in some numerical listings of ranges, somelower limits listed may be greater than some upper limits listed. Oneskilled in the art will recognize that the selected subset will requirethe selection of an upper limit in excess of the selected lower limit.

Wood Laminate Structures

In some embodiments, a wood laminate of the present invention maycomprise a plurality of wood substrates and a substituted celluloseester adhesive (“SCE-adhesive”) disposed between at least a portion ofat least two of the wood substrates.

As used herein, the terms “substituted cellulose ester adhesive” and“SCE-adhesive” refer to an adhesive composition that comprises asubstituted cellulose ester. As used herein, the term “substitutedcellulose ester” refers to a polymeric compound having a cellulosepolymer backbone having an organic ester substituent and an inorganicester substituent. Further, the term “inorganic ester substituent”refers to an ester that comprises an oxygen bound to an R group and aninorganic, nonmetal atom (e.g., sulfur, phosphorus, boron, andchlorine). It should be noted that inorganic esters encompass estersderived from oxoacids that comprise both inorganic, nonmetal atoms andcarbon atoms, e.g., alkyl sulfonic acids like methane sulfonic acid.Details of SCE-adhesives suitable for use in conjunction with woodlaminates of the present invention are described further herein.

Examples of wood substrates suitable for use in conjunction with woodlaminates of the present invention may include, but are not limited to,both wood and/or grass derived materials like wood veneers, particleboard, fiberboard, medium-density fiberboard, high-density fiberboard,oriented strand board, cork, hardwoods (e.g., balsa wood, beech, ash,birch, Brazil wood, cherry, chestnut, elm, hickory, mahogany, maple,oak, rosewood, teak, walnut, locust, mango, alder, and the like),softwoods (e.g., pine, fir, spruce, cedar, hemlock, and the like), roughlumber, finished lumber, natural fibrous material, bamboo, and anycombination thereof. As used herein, the term “wood veneer” refers to athin slice of wood, typically thinner than about 4 mm. In someembodiments, a wood veneer may be a hard, high quality wood such ascherry.

Wood substrates suitable for use in conjunction with wood laminates ofthe present invention may have any cross-sectional shape including, butnot limited to, circular, substantially circular, ovular, substantiallyovular, square, rectangular, trapezoidal, polygonal, polygonal withrounded edges, and any hybrid thereof.

In some embodiments, a wood laminate of the present invention maycomprise a plurality of wood substrates in any suitable configuration.Examples of suitable configurations may include, but are not limited to,those illustrated in FIG. 1. FIG. 1A illustrates two wood substrates 101and 102 in a stacked configuration. FIG. 1B illustrates two woodsubstrates 103 and 104 in a side-by-side configuration. FIG. 1Cillustrates a plurality of wood substrates in a hybrid configuration,wherein wood substrates 105 and 106 are in a side-by-side configurationthat mate at an angle, wood substrate 107 is shown disposed on top ofwood substrates 105 and 106, and wood substrate 108 is shown disposedbelow wood substrates 105 and 106. FIG. 1D illustrates a plurality ofwood substrates in a complex configuration where wood substrates 109,110, 111, and 112 are in a side-by-side configuration and have disposedthereabout a collection of wood substrates that include a bottom woodsubstrate 113, a top wood substrate 114, two side wood substrate 115 and116, and four corner wood substrates 117, 118, 119, and 120. FIG. 1Eillustrates a plurality of wood substrates where wood substrates 121,122, and 123 are in a stacked configuration with a bottom wood substrate123, a top wood substrate 122, and wood substrate 121 disposedtherebetween. One skilled in the art with the benefit of this disclosureshould recognize that FIGS. 1A-1E are merely examples of possibleconfigurations of wood substrates for use as, for example, a woodlaminate, and that a multitude of other configurations are possible andwithin the bounds of this disclosure.

In some embodiments, at least a portion of a product may comprise woodlaminates of the present invention. Although wood laminates of thepresent invention may be used in any product in which it is suitable touse a wood laminate, examples of products suitable to be or haveincluded therein a wood laminate of the present invention may include,but are not limited to, plywood, furniture or components thereof (e.g.,desks, bed rails, headboards, shelving, drawers, cabinets, chests,chairs, ladders, or stools), doors, flooring, moldings, wood trim (e.g.,decorative household trim or automotive wood trim), wood paneling,picture frames, window frames, I-beams, and the like.

By way of nonlimiting example, a wood laminate of the present inventionmay be plywood that comprises a plurality of wood substrates, preferablywood veneers, in a layered configuration with an SCE-adhesive disposedbetween at least a portion of two of the wood substrates. In somepreferred embodiments, the SCE-adhesive may be used as the primaryadhesive in the plywood. In some preferred embodiments, the SCE-adhesivemay be at least substantially formaldehyde-free.

By way of another nonlimiting example, a wood laminate of the presentinvention may be a piece of furniture that comprises a plurality of woodsubstrates (e.g., fiberboard and wood veneer) and an SCE-adhesivedisposed between at least a portion of two of the wood substrates. Insome embodiments where the wood substrates include at least fiberboardand wood veneer, such that the fiberboard may provide at least some ofthe structural integrity, and the wood veneer may provide a visually andtexturally appealing outer surface. In some preferred embodiments, theSCE-adhesive may be used as the primary adhesive in the piece offurniture. In some preferred embodiments, the SCE-adhesive may be atleast substantially formaldehyde-free.

By way of yet another nonlimiting example, a wood laminate of thepresent invention may be a bed headboard that comprises a plurality ofwood substrates (e.g., at least two lumber pieces in a side-by-sideconfiguration (e.g., as shown in FIG. 1B)) and an SCE-adhesive disposedbetween at least a portion of two of the wood substrates. Further, theplurality of wood substrates may, in some embodiments, further includewood veneer that is disposed on at least a portion of the plurality oflumber pieces, wherein an SCE-adhesive is disposed between at least aportion of the plurality of lumber pieces and at least a portion of thewood veneer. In some preferred embodiments, the SCE-adhesive may be usedas the primary adhesive in the headboard. In some preferred embodiments,the SCE-adhesive may be at least substantially formaldehyde-free.

By way of yet another nonlimiting example, the wood laminate of thepresent invention may be a piece of flooring comprising a plurality ofwood substrates (e.g., wood veneers) in a layered configuration having atop wood substrate that provides a visually and texturally appealingouter surface, wherein an SCE-adhesive is disposed between at least aportion of two of the wood substrates. In some preferred embodiments,the SCE-adhesive may be used as the primary adhesive in the piece offlooring. In some preferred embodiments, the SCE-adhesive may be atleast substantially formaldehyde-free.

By way of another nonlimiting example, the wood laminate of the presentinvention may be wood trim (e.g., for use in a home or automobile) thatcomprises at least two wood substrates (e.g., particle board and woodveneer having a visually appealing outer surface (e.g., the grainstructure of oak)), wherein an SCE-adhesive is disposed between at leasta portion of two of the wood substrates. In some preferred embodiments,the SCE-adhesive may be used as the primary adhesive in the wood trim.In some preferred embodiments, the SCE-adhesive may be at leastsubstantially formaldehyde-free.

Substituted Cellulose Ester Adhesive Compositions

As described above, the terms “substituted cellulose ester adhesive” and“SCE-adhesive” refer to an adhesive composition that comprises asubstituted cellulose ester, where the term “substituted celluloseester” refers to a polymeric compound having a cellulose polymerbackbone having an organic ester substituent and an inorganic estersubstituent. Further, the term “inorganic ester substituent” refers toan ester wherein the ether linkage of the ester comprises an oxygenbound to an R group and an inorganic, nonmetal atom (e.g., sulfur,phosphorus, boron, and chlorine). It should be noted that inorganicesters encompass esters derived from oxoacids that comprise bothinorganic, nonmetal atoms and carbon atoms, e.g., alkyl sulfonic acidslike methane sulfonic acid.

Organic ester substituents of a substituted cellulose ester describedherein may include, but are not limited to, C₁-C₂₀ aliphatic esters(e.g., acetate, propionate, or butyrate), aromatic esters (e.g.,benzoate or phthalate), substituted aromatic esters, and the like, anyderivative thereof, and any combination thereof.

In some embodiments, the degree of substitution of the organic estersubstituents of a substituted cellulose ester described herein may rangefrom a lower limit of about 0.2, 0.5, or 1 to an upper limit of lessthan about 3, about 2.9, 2.5, 2, or 1.5, and wherein the degree ofsubstitution may range from any lower limit to any upper limit andencompass any subset therebetween.

Inorganic ester substituents of a substituted cellulose ester describedherein may include, but are not limited to, hypochlorite, chlorite,chlorate, perchlorate, sulfite, sulfate, sulfonates (e.g., taurine,toluenesulfonate, C₁-C₁₀ alkyl sulfonate, and aryl sulfonate),fluorosulfate, nitrite, nitrate, phosphite, phosphate, phosphonates,borate, and the like, any derivative thereof, and any combinationthereof.

In some embodiments, the weight percent of the inorganic, nonmetal atomof the inorganic ester substituent of a substituted cellulose esterdescribed herein may range from a lower limit of about 0.01%, 0.05%, or0.1% to an upper limit of about 8%, 5%, 3%, 1%, 0.5%, 0.25%, 0.2%, or0.15%, and wherein the weight percent may range from any lower limit toany upper limit and encompass any subset therebetween.

Substituted cellulose esters for use in conjunction with an SCE-adhesivedescribed herein may be derived from any suitable cellulosic source.Suitable cellulosic sources may include, but are not limited to,softwoods, hardwoods, cotton linters, switchgrass, bamboo, bagasse,industrial hemp, willow, poplar, perennial grasses (e.g., grasses of theMiscanthus family), bacterial cellulose, seed hulls (e.g., soy beans),recycled cellulose, and the like, and any combination thereof.Unexpectedly, it has been discovered, and is described further herein,that the adhesive properties of SCE-adhesives may have a relationshipto, inter alia, the cellulosic source from which the substitutedcellulose esters are derived. Without being limited by theory, it isbelieved that other components, e.g., lignin and hemicelluloses, andconcentrations thereof in the various cellulosic sources contribute tothe differences in adhesive properties of the substituted celluloseesters derived therefrom. By way of nonlimiting example, a softwood mayyield an SCE-adhesive with higher binding strength as compared to anSCE-adhesive derived from a hardwood.

In some embodiments, substituted cellulose esters described herein, andconsequently SCE-adhesives and articles produced therewith, may bedegradable, including biodegradable and/or chemically degradable.Without being limited by theory, it is believed that at least someinorganic ester substituents may be more susceptible to hydrolysis thana corresponding cellulose ester that does not comprise (or minimallycomprises) inorganic ester substituents. Further, after some inorganicester substituents undergo hydrolysis, a strong acid may be produced,which may further speed degradation.

In some embodiments, an SCE-adhesive suitable for use in conjunctionwith wood laminates of the present invention may comprise at least onesubstituted cellulose ester and a solvent. Suitable solvents for use inconjunction with an SCE-adhesive described herein may include, but arenot limited to, water, acetone, methanol, ethanol, methylethyl ketone,methylene chloride, dioxane, dimethyl formamide, tetrahydrofuran, aceticacid, dimethyl sulfoxide, N-methyl pyrrolidinone, dimethyl carbonate,diethyl carbonate, ethylene carbonate, propylene carbonate, and thelike, any derivative thereof, and any combination thereof. By way ofnonlimiting example, an SCE-adhesive described herein may comprise atleast one substituted cellulose ester having an organic estersubstituent degree of substitution of greater than about 0 to about 1,an aqueous solvent, and optionally an organic solvent. By way of anothernonlimiting example, an SCE-adhesive described herein may comprise atleast one substituted cellulose ester having an organic estersubstituent degree of substitution of about 0.7 to about 2.7 and a mixedsolvent that comprises an aqueous solvent and an organic solvent (e.g.,acetone). By way of yet another nonlimiting example SCE-adhesives of thepresent invention may, in some embodiments, comprise at least onesubstituted cellulose ester having an organic ester substituent degreeof substitution of about 2.4 to less than about 3, an organic solvent(e.g., acetone), and optionally an aqueous solvent at about 15% or lessby weight of the organic solvent.

In some embodiments, an SCE-adhesive suitable for use in conjunctionwith wood laminates of the present invention may be formaldehyde-free,which may also be described as “an adhesive with no added formaldehyde.”In some embodiments, an SCE-adhesive for use in conjunction with woodlaminates of the present invention may be substantiallyformaldehyde-free, i.e., comprise less than 0.01% formaldehyde by weightof the substituted cellulose acetate of the SCE-adhesive composition.

In some embodiments, SCE-adhesives suitable for use in conjunction withwood laminates of the present invention may further comprise anadditive. Additives suitable for use in conjunction, with SCE-adhesivesdescribed herein may include, but are not limited to, plasticizers,crosslinkers, insolubilizers, starches, fillers, thickeners, rigidcompounds, water resistance additives, flame retardants, lubricants,softening agents, antibacterial agents, antifungal agents, pigments,dyes, and any combination thereof.

Plasticizers may, in some embodiments, allow for tailoring the viscosityand/or affecting adhesive properties of SCE-adhesives described herein.Examples of plasticizers suitable for use in conjunction withSCE-adhesives described herein may include, but are not limited to,glycerin, glycerin esters, polyethylene glycol, diethylene glycol,polypropylene glycol, polyglycoldiglycidyl ethers, dimethyl sulfoxide,alkylphosphate esters, polycaprolactone, triethyl citrate, acetyltrimethyl citrate, dibutyl phthalate, diaryl phthalate, diethylphthalate, dimethyl phthalate, di-2-methoxyethyl phthalate, dibutyltartrate, ethyl o-benzoylbenzoate, ethyl phthalyl ethyl glycolate,methyl phthalyl ethyl glycolate, n-ethyltoluenesulfonamide, triacetin,triacetin, o-cresyl p-toluenesulfonate, trimethyl phosphate, triethylphosphate, tributyl phosphate, triphenyl phosphate, tripropionin,polycaprolactone, and the like, any derivative thereof, and anycombination thereof.

Crosslinkers may, in some embodiments, increase the adhesive propertiesand/or increase water resistance of SCE-adhesives described herein.Examples of crosslinkers suitable for use in conjunction with anSCE-adhesive described herein may, in some embodiments, include, but arenot limited to, Lewis-acidic salts (e.g., magnesium salts, aluminumsalts, and zirconium salts, and in particular chloride and nitrate saltsthereof), boric acid, borate salts, phosphate salts, ammonium zirconiumcarbonate, potassium zirconium carbonate, metal chelates (e.g.,zirconium chelates, titanium chelates, and aluminum chelates),formaldehyde crosslinkers, polyamide epichlorohydrin resin, crosslinkerslike urea glyoxal adducts and alkylates thereof (e.g., methylatedglyoxal adducts and N-methylolated glyoxal adduct derivatives),crosslinkers containing N-methylol groups, crosslinkers containingetherified N-methylol groups, and the like, any derivative thereof, andany combination thereof. Additional crosslinker examples may includeN-hydroxymethyl-reactive resins like1,3-dimethylol-4,5-dihydroxyimidazolidinone(4,5-dihydroxy-N,N′-dimethylolethyleneurea) or their at least partlyetherified derivatives (e.g., derivatives with hydroxymethylated cyclicethyleneureas, hydroxymethylated cyclic propyleneureas,hydroxymethylated bicyclic glyoxal diureas, and hydroxymethylatedbicyclic malonaldehyde diureas). Examples of at least partly etherifiedderivatives of hydroxymethylated cyclic ethyleneureas may include, butare not limited to, ARKOFIX® products (e.g., for example ARKOFIX® NECplus or ARKOFIX® NES (ultra-low formaldehyde crosslinking agents,available from Clariant SE Switzerland), glyoxal, urea formaldehydeadducts, melamine formaldehyde adducts, phenol formaldehyde adducts,hydroxymethylated cyclic ethyleneureas, hydroxymethylated cyclicthioethyleneureas, hydroxymethylated cyclic propyleneureas,hydroxymethylated bicyclic glyoxal diurea, hydroxymethylated bicyclicmalonaldehyde diureas, polyaldehydes (e.g., dialdehydes), protectedpolyaldehydes (e.g., protected dialdehydes), bisulfite protectedpolyaldehydes (e.g., bisulfite protected dialdehydes), isocyanates,blocked isocyanates, dimethyoxytetrahydrafuran, dicarboxylic acids,epoxides, diglycidyl ether, hydroxymethyl-substituted imidazolidinone,hydroxymethyl-substituted pyrimidinones, hydroxymethyl-substitutedtriazinones, oxidized starch, oxidized polysaccharides, oxidizedhemicellulose, and the like, any derivative thereof, and any combinationthereof. Combinations of any of the foregoing examples may also besuitable. For example, hydroxymethylated compounds, at least partlyetherified derivatives of hydroxymethylated compounds, dialdehyde-basedcompounds, and/or capped dialdehyde compounds may be useful incombination with Lewis-acidic salts. One skilled in the art with thebenefit of this disclosure should understand that formaldehydecrosslinkers should be excluded from use in conjunction withformaldehyde-free SCE-adhesives, and limited in substantiallyformaldehyde-free SCE-adhesives.

Insolubilizer additives may, in some embodiments, increase thehydrophobic nature of the adhesive. Examples of insolubilizer additivesfor use in conjunction with SCE-adhesives described herein may, in someembodiments, include, but are not limited to, copolymers of polyvinylalcohol and polyvinyl acetate, glyoxal, glycerin, sorbitol, dextrine,alpha-methylglucoside, and the like, and any combination thereof.

Water resistance additives may, in some embodiments, increase the waterresistance properties of SCE-adhesives described herein, which mayconsequently yield wood laminates capable of maintaining theirmechanical properties in environments with higher water concentrations,e.g., humid environments. Examples of water resistance additives for usein conjunction with SCE-adhesives described herein may include, but arenot limited to, waxes, polyolefins, insolubilizers, or combinationsthereof.

Fillers may, in some embodiments, increase the rigidity of SCE-adhesivesdescribed herein, which may consequently increase the mechanicalrigidity of a wood laminate produced therewith. Fillers suitable for usein conjunction with SCE-additives described herein may include, but arenot limited to, coconut shell flour, walnut shell flour, wood flour,wheat flour, soybean flour, gums, starches, protein materials, calciumcarbonate, zeolite, clay, rigid compounds (e.g. lignin), thickeners, andthe like, and any combination thereof.

Flame retardants suitable for use in conjunction with SCE-additivesdescribed herein may include, but are not limited to, silica,organophosphates, polyhalides, and the like, and any combinationthereof.

In some embodiments, SCE-adhesives described herein may be characterizedas having a solids content (contributed to, at least in part, by someadditives) ranging from a lower limit of about 4%, 8%, 10%, 12%, or 15%,to an upper limit of about 75%, 50%, 45%, 35%, or 25%, and wherein thesolids content may range from any lower limit to any upper limit andencompass any subset therebetween.

In some embodiments, a wood laminate of the present invention maycomprise a plurality of wood substrates (e.g., any wood substratedisclosed herein including combinations thereof) and SCE-adhesives,according to any embodiments disclosed herein, disposed between at leasta portion of at least two of the wood substrates. SCE-adhesives may, insome embodiments, comprise substituted cellulose esters according to anyembodiment disclosed herein, optionally solvent, and optionally anyadditives. Substituted cellulose esters may, in some embodiments,comprise a polymeric compound having a cellulose polymer backbone havingan organic ester substituent and an inorganic ester substituent and haveat least one characteristic selected from the group consisting of atleast one organic ester substituent according to those described herein,an organic ester substituent degree of substitution from about 0.2 toless than about 3, at least one inorganic ester substituent according tothose described herein, a weight percent of the inorganic, nonmetal atomof the inorganic ester substituent between about 0.01% and about 1%,being derived from a cellulose material described herein, and anycombination thereof.

Substituted cellulose esters described herein may be produced utilizingone of several synthesis routes that, in some embodiments, comprise ahydrolysis reaction where water and inorganic ester oxoacid catalystsare added to a cellulose ester mixture so as to yield the substitutedcellulose esters. The synthesis of substituted cellulose estersdescribed herein is described in further detail in copendingInternational Patent Application No. PCT/US12/56802 entitled“Substituted Cellulose Ester Adhesives and Methods and Articles RelatingThereto” filed on the same day as the present application, the entiredisclosure of which is incorporated herein by reference. Threenonlimiting examples of synthesis routes are illustrated in FIGS. 2-4.

Referring now to FIG. 2, in some embodiments, a cellulosic material mayundergo (2.1) an activation reaction that swells the cellulosic materialin the presence of an activating agent so as to make internal surfacesaccessible for subsequent reactions, (2.2) an esterification reaction inthe presence of an inorganic ester oxoacid catalyst and an organicesterification reactant so as to yield a cellulose ester mixture, and(2.3) a hydrolysis reaction in the presence of water and additionalinorganic ester oxoacid catalyst so as to yield substituted celluloseesters. In some embodiments, the substituted cellulose esters may thenoptionally be further processed, e.g., to yield purified substitutedcellulose esters. In some embodiments, the inorganic ester oxoacidcatalyst of the (2.2) esterification reaction and the (2.3) hydrolysisreaction may be the same or different inorganic ester oxoacid catalysts.

Referring now to FIG. 3, in some embodiments, synthesis of substitutedcellulose esters may begin with the cellulose ester starting material,e.g., cellulose acetate. As shown in FIG. 3, a cellulose ester mixture(e.g., a swollen cellulose acetate in acetic acid) may undergo (3.1) ahydrolysis reaction in the presence of water, an inorganic ester oxoacidcatalyst, and an organic esterification reactant, so as to yieldsubstituted cellulose esters that may optionally be further processed.

Referring now to FIG. 4, in some embodiments, synthesis of substitutedcellulose esters may begin with a cellulose sulfate, cellulosephosphate, and/or cellulose nitrate starting material. As shown in FIG.4, the cellulose sulfate, cellulose phosphate, and/or cellulose nitratestarting material may undergo (4.1) an esterification reaction in thepresence of an inorganic ester oxoacid catalyst and an organicesterification reactant so as to yield a cellulose ester mixture, andoptionally (4.2) a hydrolysis reaction in the presence of additionalinorganic ester oxoacid catalyst so as to yield substituted celluloseesters that may optionally be further processed. In some embodiments,the (4.2) hydrolysis reaction may optionally further utilize water, asillustrated in FIG. 4. In some embodiments, the inorganic ester oxoacidcatalyst of (4.1) an esterification reaction and optionally (4.2) ahydrolysis reaction may be the same or different inorganic ester oxoacidcatalysts. One skilled in the art, with the benefit of this disclosure,should recognized that (4.2) the hydrolysis reaction is optional in thissynthesis scheme as the starting material has inorganic estersubstituents, some of which may be converted to organic estersubstituents in (4.1) the esterification reaction, thereby yielding asubstituted cellulose ester described herein.

As illustrated in the nonlimiting examples above, in some embodiments,the synthesis of substituted cellulose esters described herein mayinvolve, inter a/ia, a hydrolysis reaction where inorganic ester oxoacidcatalysts, water, and optionally other reactants are added to acellulose ester mixture so as to yield the substituted cellulose esters.Further, it should be noted that in the nonlimiting examples above, thevarious chemical components may be mixed and/or added to thecorresponding material and/or mixture in a plurality of sequences thatmay including multiple additions of any chemical component. In somepreferred embodiments, hydrolysis reactions that include organicesterification reactants may be carried with adding the water after theinorganic ester oxoacid catalyst and the organic esterificationreactant, so as to minimize potentially deactivating reactions betweenthe water and the other reactants or intermediates thereof. In somepreferred embodiments, hydrolysis reactions that do not include organicesterification reactants may be carried with concurrent addition of thewater and the inorganic ester oxoacid catalyst, so as to minimize anypotential degradation of the cellulose ester mixture by the inorganicester oxoacid catalyst.

Methods of Making Wood Laminate Compositions

In some embodiments, producing a wood laminate of the present inventionmay involve applying an SCE-adhesive to at least a portion of a surfaceof a first wood substrate; placing a second wood substrate in contactwith the portion of the surface of the first wood substrate; and dryingthe SCE-adhesive.

In some embodiments, producing the wood laminate may further compriseapplying an SCE-adhesive to at least a portion of the second woodsubstrate that contacts the portion of the surface of the first woodsubstrate.

In some embodiments, applying an SCE-adhesive to a wood substrate mayinvolve: painting, rolling, smearing, spreading, squeezing, spraying,atomizing, dotting, any hybrid thereof, and any combination thereof,either continuously or intermittently.

In some embodiments, drying an SCE-adhesive described herein mayinvolve: allowing time to pass, pulling vacuum, applying an air force,applying heat, applying pressure, and any combination thereof. In someembodiments, applying pressure may be static (e.g., using a c-clamp),moving (e.g., between rollers), any hybrid thereof, and any combinationthereof, either continuously or intermittently.

To facilitate a better understanding of the present invention, thefollowing examples of preferred or representative embodiments are given.In no way should the following examples be read to limit, or to define,the scope of the invention.

EXAMPLES Example 1

Three substituted cellulose esters and two cellulose esters wereproduced and analyzed. Cellulose was treated with acetic acid and thenmixed with a cooled solution of acetic acid, acetic anhydride, andsulfuric acid. The temperature of the resultant mixture was increasedand allowed to react for about 20 minutes. At this point, celluloseester compositions were hydrolyzed. To produce substituted celluloseesters, the mixture was hydrolyzed in the presence of additionalsulfuric acid. Table 1 below provides the conditions for the productionof the five samples.

TABLE 1 Acetyl Value Sulfur SO₄ (% as Content Content Time Temp (° C.)acetic acid) (ppm) (ppm) CA-1 6 73.0 39.03 105 314 CA-2 4.5 75.0 40.15160 481 SCA-1 6 65.0 41.43 807 2419 SCA-2 4.5 70.0 38.02 268 805 SCA-34.5 68.5 39.08 429 1286

This example is thought to demonstrate that substituted cellulose esters(specifically, substituted cellulose acetates) can be produced with highsulfur contents at relatively low temperatures and short hydrolysistimes that are comparable to standard cellulose acetate hydrolysistimes, which is advantageous in the commercial-scale production ofsubstituted cellulose esters.

Example 2

Several adhesive compositions (Adhesives 1-5) having varied solvents andsubstituted cellulose acetate compositions were tested for theiradhesive properties in a variety of wood laminates. Further, two woodlaminates were produced and analyzed with commercially available ELMER'SGLUE ALL® (a polyvinyl acetate)-based adhesive, available from Elmer'sProducts, Inc.). Table 2 provides the wood laminate compositions, andTable 3 provides the results of Lap Shear tests conducted using INSTRON®(Model 3366) as a measure of the adhesive properties of the variousadhesive compositions.

Upon visual inspection, the substituted cellulose acetate adhesives ofthis example were optically clear and had a high gloss, which may bedesirable in some commercial applications.

To form the laminates, two small wooden blocks- or two cardboard pieceswere glued together using a 10% aqueous solution of the Adhesives 1-5(Table 2) or ELMER'S GLUE ALL® (as noted) and allowed to dry. Theresulting laminates were difficult to separate (i.e., none of the blocksbroke in the tensile testing setup used or the cardboard failed beforethe adhesive bond). When enough force was applied to separate theblocks, the wood fibers broke which suggests that the substitutedcellulose acetate adhesive is at least as strong as the wood fibers.

TABLE 2 Solvent Solids Sulfur Sample Adhesive System (wt %) (mg/kg)Substrate Drying 1 ELMER'S emulsion 54 — cardboard 1 hr GLUE ALL ®(ambient) 2 Adhesive 1 aqueous 10 not cardboard 1 hr measured (ambient)3 Adhesive 2 aqueous 20 4940 wood 2.25 hr   (ambient) 4 Adhesive 3aqueous 15 4530 wood 2.25 hr   (ambient) 5 Adhesive 4 mixed 10 4940 wood2.25 hr   organic/ (ambient) aqueous 6 Adhesive 2 aqueous 15 4940 wood2.25 hr   (ambient) 7 ELMER'S emulsion 27 — wood overnight GLUE ALL ®(ambient) 8 Adhesive 5 aqueous 10 5570 wood 1 hr (120° C.) 9 Adhesive 5aqueous 10 5570 wood 1 hr (120° C.) 10 Adhesive 5 aqueous 10 5570 wood 1hr (120° C.)

TABLE 3 Break Sam- Additional Point ple Adhesive Substrate Treatment(kgf) Comments 1 ELMER'S cardboard 58.94 paper failure GLUE ALL ® 2Adhesive 1 cardboard 43.86 paper failure 3 Adhesive 2 wood >107 exceededload cell capacity 4 Adhesive 3 wood >107 exceeded load cell capacity 5Adhesive 4 wood >107 exceeded load cell capacity 6 Adhesive 2 wood >107exceeded load cell capacity 7 ELMER'S wood >107 exceeded load GLUE ALL ®cell capacity 8 Adhesive 5 wood >107 exceeded load cell capacity 9Adhesive 5 wood 1 hr >107 exceeded load (4° C.) cell capacity 10Adhesive 5 wood 1 hr >107 exceeded load (4° C.) cell capacity

It is believed that this example demonstrates, among many things, thatsubstituted cellulose acetates with high sulfur content are effective asan adhesive on a variety of substrates.

Example 3

Various additives were added to three adhesive compositions thatcomprise substituted cellulose acetate according to at least someembodiments described herein. The resulting compositions were tested fortheir adhesive properties on wood substrates (¼″ pine strips 1.5″ inwidth) using INSTRON® (Model 3366) Lap Shear test. Summaries of theresults are shown below in Tables 4 and Table 5.

Adhesive 6 comprises substituted cellulose acetate having about 620mg/kg of sulfur. To the Adhesive 6, varying amounts of ammoniumzirconium carbonate were added. Table 4 provides the results of the LapShear test for the various compositions.

TABLE 4 % Zr by wt of total solution Average Average Stnd. (% Zr by wtof solids) Break (kgf)* Break (psi)** Dev.  0 (0) 179 263 32 0.04%(0.2%) 271 398 110 0.08% (0.4%) 280 411 35 0.16% (0.9%) 300 441 71 0.32%(1.8%) 362 532 45 *average of 6 replicates **lap shear of 1.5″ × 1″adhered area

Adhesives 7 and 8 comprise substituted cellulose acetates having about520 mg/kg of sulfur and about 557 mg/kg of sulfur, respectively. To theAdhesives 7 and 8, varying amounts of additives were added. Table 5provides the results of the Lap Shear test for the various compositions.

TABLE 5 Adhesive 7 Adhesive 8 Break Point Break Point Additive (kgf)(kgf) no additive 225 349 ammonium zirconium 348 245 carbonate (14% bywt of solids) polyvinyl acetate (MW 271 210 ~140,000) (14% by wt ofsolids) polyvinyl alcohol (MW not tested 154 ~150,000) (14% by wt ofsolids)

As shown in Table 4, the addition of zirconium can increase the strengthrequired to break the bond formed by substituted cellulose esteradhesives. Further, Table 5 demonstrates the use of other polymer asplasticizer in substituted cellulose ester adhesives, which mayadvantageously allow for tailoring the adhesive strength of suchcompositions.

Example 4

A plurality of adhesives samples were prepared by adding 8% by weight ofa substituted cellulose acetate having about 1286 mg/kg sulfur to thedesired solvent system as outlined in Table 6. The adhesive samples weremixed overnight. The crosslinkers (if applicable) were added in amountsoutlined in Table 6, and the adhesive samples were mixed for about 2minutes. The adhesive samples were used to adhere two blocks of pinewood together and allowed to dry for 15 minutes at 120° C. The Lap Sheartest for was tested as described in Example 2.

TABLE 6 Break Point Adhesive Solvent Crosslinker (kgf) 9 6 parts ethanolnone 182.68 10 4 parts water NES* (1%**) 227.88 11 ZA* (0.5%) 242.38 127 parts water none 161.45 13 2 parts ethanol NES (1%) 310.38 14 1 partacetone ZA (0.5%) 145.10 15 4 parts water none 109.60 16 1 part ethanolNES (1%) 202.96 17 5 parts acetone ZA (0.5%) 134.14 18 8 parts waternone 138.89 19 1.5 parts dimethyl carbonate NES (1%) 189.30 20 0.5 partsacetone NES (4%) 379.44 21 ZA (0.5%) 285.12 22 ZA (1%) 349.53 23 7 partswater none 175.99 24 2 parts dimethyl carbonate NES (1%) 167.71 25 1part acetone AZC* (1%) 294.87 *NES is modified dimethylol dihydroxyethylene urea (available as ARKOFIX ® NES from Clariant), ZA iszirconium acetate, and AZC is ammonium zirconium carbonate.**Crosslinker concentrations are by weight of the solids content of thesample.

This example demonstrates that both the crosslinker and the solventsystem may affect the adhesive properties of substituted cellulose esteradhesives, which may allow for two additional handles that can beutilized in tailoring the adhesive properties for substituted celluloseester adhesives for the desired application.

Example 5

A plurality of adhesives samples were prepared by adding 12% by weightof a substituted cellulose acetate having about 997 mg/kg sulfur to thedesired solvent system as outlined in Table 7. The adhesive samples weremixed overnight. The adhesive samples were used to adhere two blocks ofpine wood together and allowed to dry for 15 minutes at 120° C. The LapShear test for was tested as described in Example 2.

TABLE 7 Solvent System dimethyl Break Point carbonate acetone waterethanol (kgf) 0 80 20 0 284.10 15 15 70 0 293.38 10 10 80 0 302.17 20 575 0 302.63 0 0 40 60 318.97 20 10 70 0 334.33 5 15 80 0 358.10 15 5 800 359.00 0 10 40 50 360.06 5 15 80 0 366.00 0 20 80 0 382.43 10 0 70 20404.86

This example demonstrates that solvent system may affect the adhesiveproperties of substituted cellulose ester adhesives, which may allow foran additional handle that can be utilized in tailoring the adhesiveproperties for substituted cellulose ester adhesives for the desiredapplication.

Example 6

A plurality of adhesives samples were prepared by adding 8% by weight ofa substituted cellulose acetate having about 1286 mg/kg sulfur to thedesired solvent system as outlined in Table 8. The adhesive samples weremixed overnight. A crosslinker of NES at 1% by weight of the solidscontent of the sample and a crosslinker catalyst ad outlined in Table 8(if applicable) at 1.5% by weight of the solids content of the samplewere added to the adhesives samples, and the adhesive samples were mixedfor about 2 minutes. The adhesive samples were used to adhere two blocksof pine wood together and allowed to dry for 15 minutes at 120° C. TheLap Shear test for was tested as described in Example 2.

TABLE 8 Break Point Adhesive Solvent Crosslinker (kgf) 26 6 partsethanol None 227.88 27 4 parts water MgCl₂ 165.69 28 AlCl₃ 174.59 29 7parts water None 310.38 30 2 parts ethanol MgCl₂ 271.45 31 1 partacetone AlCl₃ 175.57 32 4 parts water None 202.96 33 1 part ethanolMgCl₂ 144.42 34 5 parts acetone AlCl₃ 140.17

This example demonstrates that a crosslinker catalyst is not required toinitiate crosslinking with the NES crosslinker, which typically doesrequire such a crosslinker catalyst. Further, such crosslinker catalystsmay reduce the adhesive properties of substituted cellulose esteradhesives.

Example 7

Two samples of substituted cellulose acetates were derived from hardwoodor softwood having about 1290 mg/kg sulfur or about 1000 mg/kg sulfur,respectively. Each substituted cellulose ester sample was used inproducing an SCE-adhesive having 12% solids and no crosslinkers in asolvent system of 60% ethanol and 40% water. The adhesive samples wereused to adhere two blocks of either pine or birch wood together andallowed to dry for 15 minutes at 120° C. The Lap Shear test for wastested as described in Example 2.

As reported in Table 9, the use of the softwood-derived celluloseacetate yielded a stronger adhesive, e.g., about 60% higher lap strengthwhen adhering pine and about 20% higher lap strength when adheringbirch, which demonstrates that the cellulosic source from which asubstituted cellulose ester is derived may affect the adhesiveproperties of the resultant SCE-adhesive.

TABLE 9 Average Stnd. Pulp Substrate Break (kgf)* Dev. hardwood pine 28010 hardwood birch 452 8 softwood pine 445 17 softwood birch 549 9*average of 2 replicates

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered,combined, or modified and all such variations are considered within thescope and spirit of the present invention. The invention illustrativelydisclosed herein suitably may be practiced in the absence of any elementthat is not specifically disclosed herein and/or any optional elementdisclosed herein. While compositions and methods are described in termsof “comprising,” “containing,” or “including” various components orsteps, the compositions and methods can also “consist essentially of” or“consist of” the various components and steps. All numbers and rangesdisclosed above may vary by some amount. Whenever a numerical range witha lower limit and an upper limit is disclosed, any number and anyincluded range falling within the range is specifically disclosed. Inparticular, every range of values (of the form, “from about a to aboutb,” or, equivalently, “from approximately a to b,” or, equivalently,“from approximately a-b”) disclosed herein is to be understood to setforth every number and range encompassed within the broader range ofvalues. Also, the terms in the claims have their plain, ordinary meaningunless otherwise explicitly and clearly defined by the patentee.Moreover, the indefinite articles “a” or “an,” as used in the claims,are defined herein to mean one or more than one of the element that itintroduces. If there is any conflict in the usages of a word or term inthis specification and one or more patent or other documents that may beincorporated herein by reference, the definitions that are consistentwith this specification should be adopted.

The invention claimed is:
 1. A wood laminate comprising: a plurality of wood substrates; and an adhesive disposed between at least a portion of two of the wood substrates, the adhesive comprising a substituted cellulose ester that comprises a cellulose polymer backbone having an organic ester substituent and an inorganic ester substituent that comprises an inorganic, nonmetal atom selected from the group consisting of sulfur, phosphorus, boron, and chlorine.
 2. The wood laminate of claim 1, wherein the substituted cellulose ester is derived from at least one selected from the group consisting of a softwood, a hardwood, a cotton linter, switchgrass, bamboo, bagasse, industrial hemp, willow, poplar, a perennial grass, bacterial cellulose, a seed hull, recycled cellulose, and any combination thereof.
 3. The wood laminate of claim 1, wherein the organic ester substituent comprises at least one selected from the group consisting of a C₁-C₂₀ aliphatic ester, an aromatic ester, any derivative thereof, and any combination thereof.
 4. The wood laminate of claim 1, wherein the inorganic ester substituent is selected from the group consisting of hypochlorite, chlorite, chlorate, perchlorate, sulfite, sulfate, a sulfonate, fluorosulfate, nitrite, nitrate, phosphite, phosphate, a phosphonate, a phosphinate, an alkyl phosphonate, borate, any derivative thereof, and any combination thereof.
 5. The wood laminate of claim 1, wherein the inorganic, nonmetal atom is present in an amount of about 0.01% or greater by weight of the substituted cellulose ester.
 6. The wood laminate of claim 1, wherein the substituted cellulose ester has a degree of substitution ranging from about 0.2 to less than about
 3. 7. The wood laminate of claim 1, wherein the adhesive further comprises a solvent comprising at least one selected from the group consisting of water, ethanol, acetone, methylethyl ketone, methylene chloride, dioxane, dimethyl formamide, methanol, tetrahydrofuran, acetic acid, dimethyl sulfoxide, N-methyl pyrrolidinone, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, and any combination thereof.
 8. The wood laminate of claim 1, wherein the adhesive further comprises an additive comprising at least one selected from the group consisting of a plasticizer, a crosslinker, an insolubilizer, a starch, a filler, a thickener, a rigid compound, a water resistance additive, a flame retardant, a lubricant, a softening agent, an antibacterial agent, an antifungal agent, a pigment, a dye, and any combination thereof.
 9. The wood laminate of claim 1, wherein the adhesive is at least substantially formaldehyde-free.
 10. The wood laminate of claim 1, wherein the wood substrate is selected from the group consisting of a wood veneer, particle board, fiberboard, medium-density fiberboard, high-density fiberboard, oriented strand board, cork, a hardwood, a softwood, rough lumber, finished lumber, natural fibrous material, bamboo, and any combination thereof.
 11. A wood laminate product comprising the wood laminate of claim 1, wherein the wood laminate product is used in at least one selected from the group consisting of plywood, furniture or a component thereof, a door, flooring, a molding, wood trim, wood paneling, a picture frame, a window frame, and an I-beam.
 12. A wood laminate comprising: a wood substrate; a wood veneer having a visually appealing surface; and an adhesive disposed between at least a portion of the wood substrate and at least a portion of the wood veneer such that at least a portion of the visually appealing surface is visible, the adhesive comprising a substituted cellulose ester that comprises a cellulose polymer backbone having an organic ester substituent and an inorganic ester substituent that comprises an inorganic, nonmetal atom selected from the group consisting of sulfur, phosphorus, boron, and chlorine.
 13. A wood laminate product comprising the wood laminate of claim 12, wherein the wood laminate product is used in at least one selected from the group consisting of plywood, furniture or a component thereof, a door, flooring, a molding, wood trim, wood paneling, a picture frame, a window frame, and an I-beam.
 14. A method comprising: providing an adhesive comprising: a substituted cellulose ester that comprises a cellulose polymer backbone having an organic ester substituent and an inorganic ester substituent that comprises an inorganic, nonmetal atom selected from the group consisting of sulfur, phosphorus, boron, and chlorine; and a solvent; and applying the adhesive to at least a portion of a surface of a first wood substrate; placing a second wood substrate to the portion of the surface of the first wood substrate; and drying the adhesive.
 15. The method of claim 14, wherein the solvent comprises about 85% or greater of an organic solvent; and wherein the substituted cellulose ester has a degree of substitution of about 2.4 to less than about
 3. 16. The method of claim 14, wherein the solvent comprises an aqueous solvent; and wherein the substituted cellulose ester has a degree of substitution of about 1 or less.
 17. The method of claim 14, wherein the solvent comprises an organic solvent and an aqueous solvent; and wherein the substituted cellulose ester has a degree of substitution of about 0.7 to about 2.7.
 18. The method of claim 14, wherein the inorganic, nonmetal atom is present in an amount of about 0.01% to about 8% by weight of the substituted cellulose ester.
 19. The method of claim 14, wherein the adhesive is at least substantially formaldehyde-free. 